Studies include an investigation of the mechanism of infection of Salmonella by certain temperate bacteriophages, particularly the steps of adsorption, ejection of DNA and penetration of nucleic acid into the cell. A second problem is related to the mechanism by which certain bacterial viruses are prevented from full development (exclusion) by the presence in Salmonella cells of a P22 prophage. We specifically wish to determine if the exclusion is due to interaction between a prophage function and the transcriptional machinery of the host cell. A third problem is a study of the association of the bacterial chromosome with the cell membrane to determine the role of the latter in replication and segregation.